The move has increased the pressure on President Muhammadu Buhari to tighten oversight over the traditional private schools known as the Almajiris, which teach millions of children in the predominantly Muslim north of the country.
Authorities released 147 students from a facility in Kaduna State on Saturday. The students, wearing maroon uniforms, were taken to a camp where the police examined their condition and contacted family members.
"No responsible democratic government would tolerate the existence of torture chambers and physical mistreatment of inmates on behalf of the rehabilitation of the victims," said Buharis spokesman Garba Shehu in a statement on Saturday.
Although Buhari's office welcomed the Nigerian police to conduct the raids, officials did not announce any changes to further regulate the facilities.
An estimated 1
0 million children attend Islamic schools in Nigeria, which for centuries were a way to become religious scholars. Teachers should promote discipline, peace and humility, and part of the training may be begging for money on the street.
Some parents pay tuition for their children to memorize the Koran. Others hope that religious leaders can help adolescents with drug addiction and mental illness in areas lacking formal health care.
However, police action has shown that the system is apparently being exploited.
"The more people rely on them, the more brutal they become," said Isa Sanusi, spokeswoman for Amnesty International in the Nigerian capital, Abuja.
Three days before the Kaduna raid, authorities rescued 500 people from an Islamic school in Katsina state, which turned out to be a rehabilitation program for young people with behavioral problems.
The men and boys who were rescued had chained to walls, beaten with sticks, and often hungry in crowded rooms, officials said. Some reported permanent sexual abuse.
They were "exposed to all forms of dehumanization," police spokesman Sanusi Buba told Voice of America.
On October 12, police released 67 men and boys from a similar facility in the same northwestern state. Photos showed victims without a shirt sitting on the floor, some with chains around their necks.
"They beat, abused and punished us every day [in] to teach us the name," said 33-year-old Lawal Ahmad to Reuters. "They do not teach us for God's sake."
On September 27, the authorities discovered 500 men and boys who lived in a house, the BBC's Kaduna Police Chief Ali Janga called the "House of Torture" investigation wave of such facilities throughout the region.
According to officials, children aged five and over were kept in chains. The police released a photo of a boy with scars on his back and arms.
Enrollment in religious education has increased as parents, who often can not afford primary education, look for alternatives that look honorable on the surface, said Matthew Page, Associate Fellow of the Chatham House Africa Program in London.
It's hard to know How widespread the problem is, he said, because data is scarce and control is weak.
"There is this absence of the state," he said, "when it comes to effectively regulating organizations like these schools." John Campbell, former US ambassador to Nigeria, said they do not prepare children for the modern economy. "Still, they provide some food and education," he said, "for over 10 million students who would otherwise have little access." either too. "